Information display circuit including means for blanking the display device

ABSTRACT

The disclosure is of a circuit which can be used in an information-handling and display system and includes a cathode glow display tube containing an anode and ten cathode electrodes which are coupled to a source of information signals in the system through a driving circuit. The driving circuit is a logic circuit which receives information signals from a decoder circuit and applies them to the cathode electrodes of the display tube, and the tube displays a number represented by the information signals when energizing potential is also applied to the tube anode. The driving circuit includes a control circuit which disables both the logic circuit and the display tube at desired times. The logic circuit includes five pairs of transistors connected in two groups with an auxiliary control transistor operating each group. The control circuit includes a transistor connected to the two control transistors for turning them off when desired to blank the display tube. A system is also disclosed for using the principles of the invention for controlling the timing of the application of information signals to the cathode electrodes and switching potentials to the anode electrodes of a series of display tubes in an informationhandling instrument.

United States Patent DECODER Primary Examiner-John W. Caldwell AssistantExaminer-Marshall M. Curtis Attorneys- Kenneth L. Miller and Robert A.Green ABSTRACT: The disclosure is of a circuit whic can be used in aninformation-handling and display system a d includes a cathode glowdisplay tube containing an anode and ten cathode electrodes which arecoupled to a source of information signals in the system through adriving circuit. The driving circuit is a logic circuit which receivesinformation signals from a decoder circuit and applies them to thecathode electrodes of the display tube, and the tube displays a numberrepresented by the information signals when energizing potential is alsoapplied to the tube anode. The driving circuit includes a controlcircuit which disables both the logic circuit and the display tube atdesired times. The logic circuit includes five pairs of transistorsconnected in two groups with an auxiliary control transistor operatingeach group. The control circuit includes a transistor connected to thetwo control transistors for turning them off when desired to blank thedisplay tube. A system is also disclosed for using the principles of theinvention for controlling the timing of the application of informationsignals to the cathode electrodes and switching potentials to the anodeelectrodes of a series of display tubes in an information-handlinginstrument.

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momaom E265 wumaom mmm zutzm utzm 555 Qmw 6mm QmN QwN Numb-2300 62 EINFORMATION DISPLAY CIRCUIT INCLUDING MEANS FOR BLANKING THE DISPLAYDEVICE BACKGROUND OF THE INVENTION Indicator tubes of the typemanufactured by Burroughs Corporation and known as NIXIE tubes have beenwidely used in information-handling systems such as computers,calculators, and the like. Under some circumstances, it is desirable topositively hold off or turn off the display tube while other parts ofthe system perform an operation or while information signals arecollected for application to the logic driver circuit for the displaytube. Various circuits have been proposed for turning off or blanking adisplay tube; however, these circuits are not completely satisfactorysince they generally operate directly on the display tube itself, andnot the associated logic circuitry. In addition, these circuits are notsuitable for use in complex systems such as computers or calculators.

SUMMARY OF THE INVENTION Briefly, a circuit embodying the inventionincludes one or more display tubes of the type described above and aseparate logic circuit for applying informations signals to each displaytube. The circuit also includes auxiliary circuit means for disablingthe logic circuit (s) and the display tube(s) at a desired time in theinformation-receiving and displaying operation DESCRIPTION OF THEDRAWING In the drawing:

FIG. I is a schematic representation of a circuit embodying theinvention; and

FIG. 2 is a schematic representation of another system embodying theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The principles of the inventionare applicable to information-handling circuits and systems whichdisplay information in a display device such as a type 6844A numericalindicator tube. Thus, the invention may be used in a relatively simplecircuit such as a decoder or in more complex systems such as computers,calculators, or the like. One type of circuit (FIG. I) which may utilizethe invention includes various information-handling circuits representedby block which feed into a decoder 30 and a display driver circuit 40.The display driver circuit 40 includes a display tube 50 and a logicdriver circuit 52 for applying thereto the output of the decoder 30 tocause a number to be displayed in tube 50.

The indicator display tube 50 is a gas-filled tube and includes 10 glowcathodes 57 in the form of numerals zero to nine and an anode electrode58. When a positive potential of about 150 volts is applied betweenanode 58 and a cathode numeral 57, the cathode exhibits cathode glow. Adriver or switch 59, which may be an electronic switch such as atransistor, is coupled to anode 58 to apply operating potential theretoat the same time that information potential is applied to a cathodenumeral.

For purposes of illustration, the decoder 30 is shown as a type whichhas seven output lines which carry signal bits having a meaning indecimal code, that is, representing a decimal number. Five lines 32comprise signal information lines, and two lines 33 comprise signalcontrol lines.

The logic driver circuit 52 for coupling signals from the decoder 36 totube 59 includes 10 signal-receiving and registering active devices 60to 69, which may be tubes, transistors, or the like. These transistorsmay be referred to as glow transistors since they are coupled to therespective glow cathodes. For purposes of illustration, three-electrodetransistors are shown with the electrodes thereof represented inconventional fashion. As shown, the devices 60 to 69 are arranged in twogroups of live and in pairs, with one member of a pair being in eachgroup. Thus, one group includes devices 60 to 64, and the other groupincludes devices 65 to 69, with the pairs being 60-65, 62-67, 63-68,64-69. In addition, two auxiliary devices 72 and 74, also transistors,are provided to control the operation of the two groups of fivetransistors.

The five transistors 60 to 64 have their emitter electrodes connectedtogether to a bus which is connected to the collector electrode ofcontrol transistor 72, and the five transistors 65 to 69 have theiremitter electrodes connected together to a bus 84 which is similarlyconnected to the collector of control transistor '74. The collectorelectrodes of the transistors 60 to 69 are each connected by leads 89 toone of the cathode numerals in tube 50. The emitter electrodes of thetwo control transistors 72 and 74 are connected together to a bus 90.

According to the invention, an auxiliary control circuit 94 is providedincluding an auxiliary control transistor 10%) which has its collectorelectrode connected to the emitter electrodes of the control transistors72 and 74 and its emitter electrode connected through a Zener diode toground. Control circuit 94 also includes a source of clock pulses orcontrol pulses coupled through a resistor and diodes M0 and (oriented asshown) the base of control or blanking transistor 100. The base oftransistor 100 is also coupled through a resistor to ground, andjunction point 18!) of the diodes 140 and 150 is connected through acapacitor to ground. A positive DC power source Vll is connected throughresistors 200 and 210 to line 33 and junction point 180, respectively,and through resistor 220 to the collector of transistor lllll. Otherconnections are made to provide bias voltages for the varioustransistors as shown and need not be described in detail. In circuit 94,capacitor 190 extends the time duration of pulses from source 120, andthe diodes 140 and 150 adjust voltage levels between source 120 and thebase of transistor 100. Under some circumstances, each diode 140 and1150 might require additional diodes to provide the desired balance, or,in some cases, no diodes may be needed.

In operation of the circuit 10, signal information is processed .throughcircuits 20 and 30, and a group of signal bits appears on the sevenlines 32 and 33. Normally, transistors 60 to 69, 72, and '74 are heldoff by the bias voltages applied. Each group of seven signal bits hassuch polarities that the base electrodes of only one pair of transistors(ill to 69 receive a positive turn-on signal and only one of the controllines 33 receives a positive turn-on signal. The positive signal appliedto the control line 33 turns on one of the control transistors, and thisin turn applies a generally negative potential to one of the buses 80 or84, and this permits one transistor of the selected pair to turn on.When the selected transistor turns on, the cathode numeral in tube 50 towhich it is connected glows and is visible when switch 59 is closed. Asa specific example, if positive potential is applied to the bases oftransistors 60 and 65 and to transistor 72, then transistor 60 is turnedon and numeral O glows.

Auxiliary control circuit 94 is used as follows. It has been found that,under some circumstances, particularly during the time when signalinformation on lines 32 and 33 is changing from one combination toanother, improper operation of tube 50 may result and two cathodes mayglow. This is prevented by the operation of the invention, In addition,the invention can be used to positively disable the circuit and thedisplay tube 50. This is accomplished, according to the invention, by anegative pulse 121 being coupled from source 120 through the resistorI30 and diodes 140 and 150, to the base of auxiliary control or blankingtransistor 100 which is normally on and is now turned off. This resultsin the application of positive potential to the emitter electrodes ofthe control transistors 72 and 74 which are also held off. Thus, agenerally positive potential is applied through the buses 80 and 84 tothe emitters of the five pairs of transistors 60 to 69 which are alsoheld off. Because all of the driving transistors 60 to 69 are immobil'ized, the indicator tube 59 is blanked or held off and no cathodes canglow.

In the circuit, the resistor 130 and capacitor 190 provide a timeconstant which determines the time duration of the control pulse 121 andthe length of time the circuit is disabled. In general, it is desirablefor the pulse to be terminated just after a new group of signal bitsappears on the lines 32 and 33 to the transistors 60 to 69 and 72, 74 sothat the information can be displayed in tube 50 without spurious glow.

The principles of the invention may also be used in a somewhat morecomplex system of the type illustrated in FIG. 2 which represents aportion of a computer, calculator, or the like in which information isdisplayed on a plurality of display tubes 50A, 50B, 50C, as is wellknown. In such a system, a single decoder 30 and logic driver circuit 52are provided for all of the display tubes, and each of the 10 outputlines 89 from circuit 52 is connected to the same cathode numeral in thedisplay tubes 50. Signal information is processed through the circuitand appears on lines 89 serially; that is, the first group of signalsrepresenting a decimal number is intended for entry in the first tube inthe series 50A, the second group of signals is intended for entry in thesecond tube 508, etc. In addition, an electronic switch means or driver59A, 59B, 59C is provided in the anode circuit of each tube 50.

A ring counter 250 is coupled to and operates each of the anode drivers59 by leads 260, and it is assumed that the signal source represented byblock includes in its circuitry a sequential memory or register fromwhich information signals are fed along toward the tubes 50. Both thering counter 260 and the memory or register in source 20 are coupled tothe output of pulse source 120 by leads 270 for synchronizing theoperation of switches 59A, 59B, and 59C and their associated displaytubes with the operation of source 20 and of decoding and drivingcircuits 30.

In operation of the system 10, the first pulse 121 from source 120operates ring counter 250 and causes the counter to apply operatingpotential to the anode of tube 59A. At the same time, the memory orregister in signal source 20 is energized by the first pulse 121 andcaused to transmit the first group of information signals through thecircuit in the direction of the indicator tubes. Again, at the sametime, the first pulse 121 energizes control circuit 94, and thiscircuit, as described above, disables logic driver circuit 52 and all ofthe indicator tubes for the length of time which is required for theinformation signals to reach lines 89. At the end of this time period,again as described above, the pulse 121 is terminated and logic drivercircuit 52 is permitted to operate and apply operating potential to oneof the cathodes in tube 59A determined by the first group of informationsignals. This selected cathode exhibits cathode glow, and the propernumeral representation appears. The next pulse 121 repeats this cycle ofoperation for tube 59B, and the third repeats the cycle of operation fortube 59C, etc.

The above-described operation occurs continuously and at such highrepetition rate that all numbers corresponding to input informationsignals are visible in their tubes 50 at the same time.

According to the invention, control circuit 94 insures the propercoordination between the feeding of information to a series of displaytubes and the operation of these tubes. In the circuits described, ifcontrol circuit 94 were not provided, spurious display might result.Such spurious display occurs when, for example, tube 59A is on anddisplaying a numeral and another group of information signals appears onlines 89 before tube 59A is turned off and the next tube 59B in theseries is switched on. When this happens, tube 59A displays two numbers.This spurious display is prevented by the invention.

I claim:

1. In a decoding system for driving at least one multiple cathodedisplay device for displaying information thereon, including a pluralityof glow transistors coupled to different cathodes, said glow transistorsbeing arranged in at least two groups, and a plurality of auxiliarytransistors, one auxiliary transistor coupled to each group forrendering said groups of transistors conductive or nonconductive whensaid auxiliary transistors are conductive or nonconductive,respectively, the improvement of a blanking circuit comprising:

a blankin transistor, said blan mg transistor being connected to likeelectrodes of said auxiliary transistors for enabling said auxiliarytransistors to be conductive or nonconductive when said blankingtransistor is conductive or nonconductive, respectively, and

means operating independently of said information for selectivelyswitching said blanking transistor between said conductive andnonconductive states,

said switching means being adapted to render said auxiliary transistorsnonconductive during the time when a change occurs in said information.

1. In a decoding system for driving at least one multiple cathodedisplay device for displaying information thereon, including a pluralityof glow transistors coupled to different cathodes, said glow transistorsbeing arranged in at least two groups, and a plurality of auxiliarytransistors, one auxiliary transistor coupled to each group forrendering said groups of transistors conductive or nonconductive whensaid auxiliary transistors are conductive or nonconductive,respectively, the improvement of a blanking circuit comprising: ablanking transistor, said blanking transistor being connected to likeelectrodes of said auxiliary transistors for enabling said auxiliarytransistors to be conductive or nonconductive when said blankingtransistor is conductive or nonconductive, respectively, and meansoperating independently of said information for selectively switchingsaid blanking transistor between said conductive and nonconductivestates, said switching means being adapted to render said auxiliarytransistors nonconductive during the time when a change occurs in saidinformation.